问题
I'm working on a project that ask the iPhone to receive data through headphone jack. I know it is doable, when I plug in the iPhone headphone it automatically change the input from the mac built in microphone to external microphone (I'm running the code on simulator) to record data. However, when I cut the headphone up and attach it to my signal generator, it seems that my mac cannot detect the external microphone anymore. Does anyone know how to manually set the headphone jack as the iPhone's input? I've searched on this topic, like link iPhone headphone jack - read in data? and hiJack project. But it seems that, once they plug in the headphone or other connecting line, the phone would automatically regard the headphone jack as the input... So I'm stuck on this problem, can anyone help? Thanks very much!
来源：https://stackoverflow.com/questions/21343496/force-iphone-to-read-in-data-through-headphone-jack